Chemotaxis of Alveolar Macrophages and Neutrophils in Response to Microbial Products Derived from Organic Dust

The inhalation of organic dust has been implicated to cause a large number of occupational lung diseases. A common event in these diseases is an inflammatory reaction affecting airway and alveolar tissue that is characterized by the recruitment of different types of inflammatory cells. Mechanisms of chemotaxis of alveolar macrophages (AMs) and neutrophils (PMNs) in response to microbial products derived from organic dust were studied. Seven agents known to be etiological agents causing respiratory symptoms (extract and endotoxin of Enterobacter agglomerans, extracts from Thermoactinomyces vulgaris and Aspergillus fumigatus, thermophilic protease, and two preparations of glucans) were used for experiments. These agents were evaluated for their ability to directly attract AMs and PMNs and to stimulate alveolar macrophages to release chemotactic factors for other AMs and PMNs. The microbial products were able to attract both AMs and PMNs directly in a dose-dependent manner and the exposure of cultured AMs to most agents were stimulatory for production of chemotactic activity for AMs and PMNs. The generation and release of this activity by AMs may provide a mechanism for the initiation and amplification of inflammatory reactions in the lung after inhalation of organic dust. Results of these in vitro studies may be relevant to the pathogenesis of alveolitis in organic dust-induced lung diseases.